Problems with Chameleon

Seven people (non disabled) from ASEL's Robotics Lab informally tested the
Chameleon robot. The purpose of the testing was for them to identify obvious
shortcomings of the system to be fixed before consumer testing begins. They were
asked to place blocks from one compartment to another, stack blocks, and do a
short version of the MSMT. Additionally, some of them tried to draw and/or write
with the Chameleon.

Definitions of table headers:

Problem: An issue that a tester mentioned as being troublesome.
Priority: A level assigned to a problem indicating the importance of a solution.
1 - important, 5 - not very important
freq: Indicates how often the problem was mentioned. 1 - not often (1 person),
2 - sometimes (2-3 people), 3 - often (greater than 3 people)
Possible Reason/s: Proposed reason/s explaining why the problem/s exists.
Possible Solution/s: Proposed solution/s to the problem/s.

Tester's Comments on Chameleon

Problem

Priority / freq.

Possible Reason/s

Possible Solution/s

1. In certain configurations, the radial master movement is difficult.

3/1

Kinematic mismatch between the master unit and person's head.

Custom make master unit for user.

2. When system is mechanically recalibrated for a particular task, a kinematic mismatch results.

3/1

The user is trying to do tasks wrt the slave, but the master and slave no longer align.

-

3. Can not disengage from master in any position without the system going unstable.

1/1

The system is not balanced throughout its full ROM. Hence, the slave drives the master to a position where the feedback loop of the radial motion takes over.

*Balance the system throughout its full ROM.

4. Some tasks are difficult without gripper pitch capability or special gripper adaptations.

3/2

Some tasks simply require this DOF.

Add this capability (controlled thru what input?).

5. Can not easily reach all items that are easily visible.

3/1

Links are not long enough or slave is positioned too far back.

The links can be made longer if system weight can be reduced to keep inertia to a minimum.

6. The master and gripper units are obtrusive and sometimes interfere with `line of sight'.

2/3

-

-

7. The master unit is ugly.

4/2

-

-

8. The system feels heavy.

1/1

Poor balancing, Too much friction is present in Bowden cables.

*Use a cable system with less friction. *Balance the mechanism throughout more of its ROM.

9. Pain at the back of the jaw and in the neck occurs.

1/2

The mouthpiece may be: too thick, too hard, not the correct shape. The load may be too large.

A Mouthstick User's Comments

There is a delay in radial motion.

One needs to be precise with tongue when operating the gripper.

A user with a head rest may have the tendency to yaw his head on the back of
the head rest rather than rotate (yaw) about the spine. The required movement
(rotation about the spine) should be described to the user.

The radial movement is not fine enough.

The gripper was rotating when intention was to open (the double sided tape
had loosened)

It may be easier to judge the system's response if all joint are powered the
same. That is, if all joints were either motor powered or body powered.

Can not achieve small movements, asp. in the powered (radial) joint. A
threshold needs to be achieved before movement occurs.

Not natural to use because of the threshold problem and not always a one to
one correspondence between input and output motions.